<form action="{$BASE_URL}" method="post">
    <input class="return" type="text" name="return" value="" required />
    <input type="hidden" name="todo" value="search" />
    <input type="text" name="q" id="user" class="search_field" required />
</form>

{literal}
<script>
    autoComplete = {
        element : '#user.search_field',
        data : {
            serviceUrl:'{/literal}{$SYS_FOLDER}{literal}services/autocomplete/user/',
            minChars:2,
            deferRequestBy: 200,
            onSelect: function(value, data){ submitQuery('#user.search_field', value,data); }
        }
    }
</script>
{/literal}
